Lipopolysaccharide increases ambient temperature preference in C57BL/6J adult mice

The hypothesis was tested that animals exposed to a potentially dangerous endotoxin would attempt to behaviorally elevate their body temperature, perhaps in an effort to engage those immunological mechanisms which would counter the adverse effects of the endotoxin. Lipopolysaccharide (LPS) from Escherichia coli injected subcutaneously (100 micrograms) in adult C57BL/6J mice increased gradient temperature preference by 2.4 degrees C over saline controls. The increase in body temperature of 1.1 degrees C after LPS injection was due to the preference for higher ambient temperatures and was not the result of a systemic reaction to LPS (animals not exposed to the gradient did not differ in body temperature). In summary, our data indicate that adult mice self-induce a febrile response, perhaps as an attempt to compensate for the physiological impact of the endotoxin.